diff --git a/masque/builder/tools.py b/masque/builder/tools.py
index 4162be3..148af4d 100644
--- a/masque/builder/tools.py
+++ b/masque/builder/tools.py
@@ -543,9 +543,10 @@ class AutoTool(Tool, metaclass=ABCMeta):
         return self
 
     @staticmethod
-    def _bend2dxy(bend: Bend, ccw: SupportsBool | None) -> tuple[NDArray[numpy.float64], float]:
+    def _bend2dxy(bend: Bend | None, ccw: SupportsBool | None) -> tuple[NDArray[numpy.float64], float]:
         if ccw is None:
             return numpy.zeros(2), pi
+        assert bend is not None
         bend_dxy, bend_angle = bend.in_port.measure_travel(bend.out_port)
         assert bend_angle is not None
         if bool(ccw):
@@ -590,6 +591,11 @@ class AutoTool(Tool, metaclass=ABCMeta):
             ) -> tuple[Port, LData]:
 
         success = False
+        # If ccw is None, we don't need a bend, but we still loop to reuse the logic.
+        # We'll use a dummy loop if bends is empty and ccw is None.
+        bends = cast(list[AutoTool.Bend | None], self.bends)
+        if ccw is None and not bends:
+            bends += [None]
 
         # Initialize these to avoid UnboundLocalError in the error message
         bend_dxy, bend_angle = numpy.zeros(2), pi
@@ -598,7 +604,7 @@ class AutoTool(Tool, metaclass=ABCMeta):
         btrans_dxy = numpy.zeros(2)
 
         for straight in self.straights:
-            for bend in self.bends:
+            for bend in bends:
                 bend_dxy, bend_angle = self._bend2dxy(bend, ccw)
 
                 in_ptype_pair = ('unk' if in_ptype is None else in_ptype, straight.ptype)
@@ -607,14 +613,16 @@ class AutoTool(Tool, metaclass=ABCMeta):
 
                 out_ptype_pair = (
                     'unk' if out_ptype is None else out_ptype,
-                    straight.ptype if ccw is None else bend.out_port.ptype
+                    straight.ptype if ccw is None else cast(AutoTool.Bend, bend).out_port.ptype
                     )
                 out_transition = self.transitions.get(out_ptype_pair, None)
                 otrans_dxy = self._otransition2dxy(out_transition, bend_angle)
 
                 b_transition = None
-                if ccw is not None and bend.in_port.ptype != straight.ptype:
-                    b_transition = self.transitions.get((bend.in_port.ptype, straight.ptype), None)
+                if ccw is not None:
+                    assert bend is not None
+                    if bend.in_port.ptype != straight.ptype:
+                        b_transition = self.transitions.get((bend.in_port.ptype, straight.ptype), None)
                 btrans_dxy = self._itransition2dxy(b_transition)
 
                 straight_length = length - bend_dxy[0] - itrans_dxy[0] - btrans_dxy[0] - otrans_dxy[0]